Abstract: The exchange energy parameter Xu of Flory new polymer solution theory could be evaluated from thermodynamic interaction parameter X which was determined by inverse gas-liquid chromatography. By using this value of X12 together with S1/S2, the ratio of contact surface area per unit characteristic volume (hard core volume) for polymer and solvent, the interaction parameters X, for polydimethylsiloxane, polyisobutylene, natural rubber and polystyrene with solvents were calculated, and plotted as X vs.2, the segment fraction of polymer. The values of X thus calculated were in good agreement with the experimental values. Moreover, the volume change in mixing VE/V0 and enthalpy of mixing corrected to infinitely dilute solution oi polymer ΔHM∞ were calculated with these parameters, and agreed with the observed values.